The Solar Neutrino Problem Neither Astrophysics No

arXiv:hep-ph/9404316v121Apr1994DOE/ER/40561-136-INT94-13-01THESOLARNEUTRINOPROBLEM:NEITHERASTROPHYSICSNOROSCILLATIONS?∗AlexeiYu.Smirnov†InstituteforNuclearTheory,UniversityofWashington,HendersonHallHN-12,Seattle,WA98195,InternationalCentreforTheoreticalPhysics,I-34100Trieste,ItalyAbstractThereisnoconsistentsolarmodelwhichcandescribeallexperimentaldataonthesolarneutrinos.Theproblemcanbeformulatedessentiallyinamodelindependentway.ThekeypointsarethecomparisonoftheHomestakeandtheKamiokandedataaswellasthecomparisonoftheGALLEXandSAGEresultswithminimalsignalestimatedfromthesolarluminosity.ItisarguedthaninsuchacomparisononeshouldusetheHomestake-IIdata(onlyafter1986)withcaution.Theresultsofthemodelindependentanalysisshowstrongsuppressionoftheberylliumneutrinoflux.Thedatacanbewelldescribedbytheresonantflavorconversion.Forthe“lowfluxmodel”whichcanaccommodatetheKamiokandesignal,aconsistentsolutioncanbefoundfortheneutrinomasssquareddifferenceΔm2=(0.3−1.0)·10−5eV2andvaluesofmixinganglesin22θ5·10−4(“verysmallmixingsolution”).∗TalkgivenattheInternationalWorkshop“Solarneutrinoproblem:AstrophysicsorOscillations”,GranSasso,Italy,February28-March1,1994†OnleavefromInstituteforNuclearResearch,RussianAcademyofSciences,117312Moscow,Russia.e-mail:[e-mail],[e-mail]11IntroductionThesolarneutrinoproblemisusuallyformulatedasdisagreementoftheexperimentalsignals[1-4]withthepredictionsofthe“reference”standardsolarmodels[5-9]‡.ThefirstGALLEXresults(1992)haveboostednewattemptstofindnon-neutrinophysicssolutionoftheproblem,andmainpointsarethefollowing.1.GALLEXandlaterSAGEsignalsexceedthesignalfromthestandardpp-neutrinofluxaswellastheminimalsignalestimatedfromtheluminosityoftheSun.Thepp-neutrinoscomposethebulkofthesolarneutrinofluxanditspredictionisthemostaccurateandreliable.Somesuppression(0.6-0.7)oftheobservedGa-signalcanberelatedtosmallerfluxesofhighenergyneutrinosforwhichthepredictionsarestronglymodeldependentandnotasreliableasforpp-neutrinos.2.KamiokandeII+IIIgives(signal)=(0.5−0.7)×(SSM),i.e.thesignalisinagreementwithpredictionwithintheoreticaluncertaintiesestimatedas∼40%.3.TheenergydistributionoftheKamiokandeeventsagreeswithundistortedenergyspectrumoftheboronneutrinos.However,theexperimentalerrorsareratherlargeandthedistortionsimpliedbyanumberofneutrinophysicssolutionsoftheproblemcannotbeexcluded.4.TheHomestakesignalafter1986isratherhigh:about3SNU.SothatthereisnodirectcontradictionbetweentheHomestakeandtheKamiokanderesults.TheboronneutrinofluxextractedfromtheHomestakedataandthefluxmeasuredbyKamiokandeagreewithinerrorbars.5.ThedifferencebetweentheHomestakeresultsbefore1986andafter1986maybejustastatisticalfluctuation.Theresultsbefore1986showtimedependencewhichcanbeduetosomeunknownsystematics.ComparingtheHomestakeandtheKamiokanderesultsoneshouldusetheHomestakedataduringthetimeofoperationoftheKamiokandeexperiment.Inthisperiodthesignalsfrombothexperimentshavenoappreciabletimedependence.6.Thereareessentialuncertaintiesintheextrapolated(tosolarenergies)cross-sectionsσ17,σ34.Somelatestexperimentalandtheoreticalstudiesindicatethatthecrosssectionscanbe30-40%belowthoseusedinthereferencemodels[10,11].‡Someauthorshoweverrefertotheproblemastotheimpossibilitytoexplainthedatawithoutintro-ducingnewneutrinoproperties.27.Thecollectiveplasmaeffectsarenottakenintoaccountappropriately.Anumberofcorrectionsmayresultindiminishingoftheopacity,andconsequently,ofthecentraltemperatureoftheSunupto2-3%[12].8.Thereareanotherunresolvedproblems(e.g.7Li-surfaceconcentration)whichmaytestifyforincompleteunderstandingofpropertiesoftheSun(innerconvection?).Thisinturn,putsthequestionmarkonthereliabilityofthesolarfluxpredictions,althoughitisunclearwhatcouldbetheimpactofthesolutionofthe7LiproblemontheinnerstructureoftheSunandonthesolarfluxes.Inthispaperwewillconsiderpresentstatusofthesolarneutrinoproblem.2Dataversuspredictions2.1Thedata1).TheaverageAr-productionrateduringallobservationtime(runs18-126)equalsafterbackgroundsubtraction[1]QAr=2.32±0.16(stat)±0.21(syst)SNU.(1)Forthepresentdiscussionitisinstructivetodividethedataintotwoparts:thedatabeforepumpbreakingin1985andafterresumingtheexperimentin1986.Forthesakeofbrevitywewillcallthedatabefore1986asdatafromHomestake-Iandafter1986asdatafromHomestake-II.Theaveragedsignalsare:QIAr=2.07±0.25SNU(Homestake−I,runs18−89)QIIAr=2.76±0.31SNU(Homestake−II,runs90−126).(2)Thelatestdatadonotconfirmtheanticorrelationwithsolaractivity:largenumberofthesunspotsin1990-1991wasaccompaniedbyhighcountingrate;relativelysmallsignalwasobservedduringquiet1992.Ontheotherhand,thedataconfirm2-3yearsperiodvariationsofsignal.AnimpressiveincreaseoftheAr-productionratehasbeenobservedinthetimeofsolarflareinJune1991.ThismaytestifyforincompleteunderstandingofthephysicsoftheSunortheHomestakeexperimentitself.2).TheboronneutrinofluxmeasuredbyKamiokandeII+IIIintheunitsΦSSM0,whereΦSSM0≡5.8·106cm−1s−1isthecentralvalueoffluxpredictedbythestandardsolarmodel[5],is[2]RII+IIIνe≡ΦexpΦSSM0=0.50±0.04(stat.)±0.06(syst.),(1σ).(3)3Thedataagreewithconstantneutrino